Pentaphosphaferrocene-mediated synthesis of asymmetric organo-phosphines starting from white phosphorus

The synthesis of phosphines is based on white phosphorus, which is usually converted to PCl3, to be afterwards substituted step by step in a non-atomic efficient manner. Herein, we describe an alternative efficient transition metal-mediated process to form asymmetrically substituted phosphines directly from white phosphorus (P-4). Thereby, P-4 is converted to [Cp*Fe(eta(5)-P-5)] (1) (Cp* = eta(5)-C-5(CH3)(5)) in which one of the phosphorus atoms is selectively functionalized to the 1,1-diorgano-substituted complex [Cp*Fe(eta(4)-P5R ' R '')] (3). In a subsequent step, the phosphine PR ' R '' R' (R ' not equal R '' not equal R' = alky, aryl) (4) is released by reacting it with a nucleophile R'M (M = alkali metal) as racemates. The starting material 1 can be regenerated with P-4 and can be reused in multiple reaction cycles without isolation of the intermediates, and only the phosphine is distilled off. Asymmetrically substituted phosphine ligands play a decisive role in catalysis, but their synthesis is rather challenging and often involves hazardous chemicals such as PCl3 or PH3. Here, the authors report the one-pot preparation of asymmetric phosphines from white phosphorus via a pentaphosphaferrocene based modular system, in which the transition metal complex can be reused.

Automated summary

The study presents an efficient method for preparing asymmetric phosphines from white phosphorus, utilizing a transition metal-mediated reaction that allows for recycling and avoids the use of hazardous chemicals.